Activated charcoal has long been known as a deodorizing agent. My prior invention shown in U.S. Reissue Pat. No. 29,504, illustrates its use in a deodorizing sheet comprising open-cell latex foam having finely ground activated charcoal homogeneously dispersed throughout the foam material. This product has been widely and effectively used in insoles to suppress disagreeable foot odor.
It has been reported in Japanese patent specifications, Nos. 61-217169 (1986) and 61-272054 (1986), that zinc oxide powder on minute nylon spheres has a strong action to decrease odor arising from the foot. Further, it has been found by an inventor of said specifications that isovaleric acid is a constant component of foot odor and that measurements of the effectiveness of zinc oxide to reduce the isovaleric acid can be used to determine the odor-reducing effectiveness of any tested zinc oxide.
Latex foam has an ingredient, zinc oxide, as shown in Example 1 of my Reissue patent, to vulcanize the latex. I have no evidence that the presence of zinc oxide in the latex reduces odor. The insoles made according to the Reissue patent are effective to reduce foot odor; however, there is a need for greater odor reduction.